A CT apparatus is a medical diagnosis apparatus to diagnose a patient with X-rays. As shown in FIG. 1, the CT apparatus includes an X-ray tube 10 which emits X-rays, a slit mechanism (optical adjustment means) 11a to adjust the width of X-rays, a bed 12 on which a patient is placed, and a detection unit 13 to detect X-rays and perform signal processing.
In general, before diagnosis using a CT apparatus, it is necessary to preheat the X-ray tube 10 to emit X-rays. During a preheat period, it is necessary to block unnecessary X-rays by using a shutter plate (X-ray blocking mechanism).
A shutter plate 11c is mounted in the optical system unit 11. The shutter mechanism 11c has a shutter plate, e.g., a lead plate, with an X-ray blocking function placed in the path of X-rays so as to implement X-ray blocking operation.
In addition, when the X-ray tube normally emits X-rays, no X-rays are blocked. At this time, the shutter plate to block X-rays moves away from the path of X-rays.
As shown in FIG. 2, the optical system unit 11 of the conventional CT apparatus includes wedge mechanisms 11a to filter X-rays, a slit mechanism 11b to adjust the width of X-rays, and the shutter plate 11c. The slit mechanism can have a plurality of types of wedges. Different types of wedges are applied to different types of diagnosis. Each wedge and the shutter plate share the same driving mechanism. A wedge and the shutter plate are moved by driving the driving mechanism to switch between different types of wedges and the shutter plates.
The conventional shutter mechanism is integrated with a wedge mechanism, and uses the driving mechanism to drive the shutter plate so as to move it to the path of X-rays along a linear rail. That is, the shutter mechanism has a complicated structure. As shown in FIG. 3, in particular, when a shutter mechanism includes only one wedge and need not control its movement, it is also necessary to the wedge mechanism driving and moving the wedge to implement switching between X-ray blockage and normal X-ray emission, resulting in increases in the amount of unwanted structure and cost.